I got this error "Invalid Hash" when installing TooManyTabs, what should I do?

This problem happens when the add-on file in Firefox Add-on platform is not copied to other mirror servers properly. As this a Firefox server error, we can't do much about it. Please refer to the details here. You can manually install the add-on by following the steps below.

• Click "Add to Firefox" or "Download it"
• When the End-User License Agreement page is shown, do not click the green button
• Right click and choose "Save Link As...", save the file to your hard disk
• Drag the file to your Firefox window and the installation should start